In general, as illustrated in FIG. 3, a developing unit in an electrophotographic image forming apparatus such as a copying machine or a printer, or the like is provided with: an image forming body 21 such as a photoreceptor which holds an electrostatic latent image; a developing roller 22 which abuts on the image forming body 21 and makes the electrostatic latent image into a visible image by attaching toner 20 supported on the surface thereof; and a toner supply roller 1 which supplies toner 20 to the developing roller 22, and an image is formed by a series of processes in which toner 20 is conveyed from a toner storing unit 23 to the image forming body 21 via the toner supply roller 1 and the developing roller 22. In the figure, the reference sign 24 indicates a layer forming blade, the reference sign 25 indicates a charging roller, the reference sign 26 indicates a transfer roller, the reference sign 27 indicates a cleaning unit, and the reference sign 28 indicates a cleaning blade.
Since a toner thin layer is needed to be uniformly formed and supported on the surface of a developing roller without unevenness in order to perform a favorable image formation in such a developing mechanism, in addition to the toner holding performance or the like of the developing roller itself, the performance of the toner supply roller, in particular, the surface performance is important. In other words, a toner supply roller is demanded to form a uniform toner layer on the surface of the developing roller by abutting on the developing roller and performing frictional electrification, supply (conveying) of toner and scraping off unneeded toner.
In order to obtain a toner supply roller having a favorable surface performance which can satisfy the above-mentioned demands, various studies have conventionally been made repeatedly. For such a toner supply roller, a foam such as polyurethane foam used as a roller member is generally known. Examples of a method for preparing polyurethane foam to be used for a toner supply roller include a method in which a urethane raw material is foamed in a mold having a desired roller shape, and a method in which a polyurethane foam having a desired roller shape is obtained by cutting out from a polyurethane block and polishing the cut-out block. In the latter method, in order to remove a fluff on the surface of the polyurethane foam which is generated in the processing, a heating processing is needed to be performed.
As a conventional technique relating to a method for manufacturing a roller, for example, Patent Document 1 discloses a method for manufacturing a roller comprising an elastic layer made of foam, the method comprising: a process for forcing the elastic layer of the roller into a cylindrical member such that it is compressed; a process for heating the outer periphery of the cylindrical member; and a process for taking the roller out from the cylindrical member. Patent Document 2 discloses a technique which uses a mold in which recessed grooves corresponding to a plurality of projecting stripes providing a predetermined concavo-convex surface structure are formed on the inner surface of the mold which forms the outer peripheral surface of a roll in a molding cavity when a toner supply roll is manufactured by foam-molding a polyurethane raw material in a molding cavity which provides a final roll shape.
Further, Patent Document 3 discloses a toner supply roller comprising a metal shaft and a urethane foam layer which is provided on the outer periphery thereof by integral molding, wherein the urethane foam layer is provided with a projection portion having a height of 10 to 200 μm on the surface thereof, and the projection portion is formed in a mold in which the metal shaft and the urethane foam layer are integrally molded. Still further, Patent Document 4 discloses a technique in which a toner conveying roller comprising a shaft body and a urethane foam layer provided on the outer periphery thereof wherein irregular concaves and convexes are formed on the outer peripheral surface of the urethane foam layer is manufactured by using a mold for manufacturing a roller in which irregular concaves and convexes are formed on the inner peripheral surface of a mold for forming a roller.